Risk of bias assessment
Only two studies included in the review (Singh et al. and Stelter et
al.) had a clear statement regarding the randomization and allocation
process. This raises concerns about the possibility of bias in the
interpretation of the review results. The complete risk of bias
assessment is summarized in Table 4.
The strength of the evidence assessed by GRADE was low to moderate due
to the small number of events, to the risk of bias of the included
studies and to the high heterogeneity among the studies (Figure 4).